In a hydraulically actuated electronically controlled fuel injection system, the injection of fuel into the cylinder is controlled by moving a poppet valve between a high pressure seat and a low pressure seat. The poppet valve member is a portion of an overall control valve that includes an electronic actuator (usually a solenoid) and various body components that include the valve seating surfaces and define the various internal fluid passageways. In part because of the requirement that the various components that make up the control valve be manufactured with realistic tolerances, performance variations in poppet valve opening and closing from one injector to another sometimes occurs. In other words, the activation and deactivation stages of different injectors sometimes diverges substantially from an expected nominal injector performance due at least in part to machining tolerances. In general, it is desirable that a group of injectors installed in a single engine all perform in a uniform and predictable manner. One way of at least partially accomplishing this goal is to ensure that the activation stage for each injector occur in a uniform and expected manner.
The fuel-injection system is operated using an activation profile map that is based upon a predicted nominal injector performance. These activation profiles are a function of different operating conditions, such as speed, load, etc. Each activation profile includes an on-time, an off-time, and a solenoid current magnitude that may vary over the duration between the on-time and the off-time. For instance, the initial current may be a pull in current, and for the remaining duration of the injection event may only be a hold current. When current is sent to an individual injector, it responds by lifting the poppet valve member to close a low pressure seat. When the solenoid current is terminated, the poppet valve member moves back toward its biased position to close a high-pressure seat. In most instances, noise is generated when the poppet valve member impacts both its low-pressure seat and the high-pressure seat.
Since the activation stage characteristics for a nominal injector are known for a given activation profile, the amount an individual injector deviates from nominal can be estimated if the activation stage characteristics of that injector can be determined. Furthermore, if the deviation of an individual injector from the nominal can be quantified, it is conceivable that the injector's performance can be brought more into line with a nominal injector by adjusting the activation profile to compensate for measured deviations due to machining tolerances and other factors.
The present invention is corrected to these and other problems associated with monitoring and adjusting the actuation stage of hydraulically actuated devices, such as fuel injectors.